Regional difference in cerebrovascular reactivity by acetazolamide in normal volunteers: A PET study with H215O

Objectives Cerebrovasular reactivity (CVR) after intravenous administration of acetazolamide (ACZ) is a marker of cerebral perfusion reserve and is employed to detect tissue at risk of cerebral infarction. However, regional difference in CVR among brain structures has not been elucidated. We aimed to investigate regional difference in CVR in normal volunteers.

Methods Twelve normal volunteers (6 males and 6 females, mean age: 50 years) underwent cerebral blood flow (CBF) measurement by means of 3D PET-CT with H215O before and after intravenous injection of ACZ. The scan was initiated 15 min after ACZ. Arterial blood was sampled from radial artery to estimate arterial input function of H215O, arterial partial pressure of CO2, hematocrit, and hemoglobin. Mean systemic blood pressure was monitored during whole procedure. Quantitative CBF images were anatomically normalized by SPM2. Absolute CBF values were read by the standard region of interest (Ibakaki M, JNM, 2008). Statistical significance (p<0.05) was tested by one-way ANOVA, Kruskal Wallis, and Bonferroni method.

Results Mean CBF for gray matter structures was 57.9 ml/100ml brain/min and 108.6 ml/100ml brain/min before and after ACZ, respectively. Mean CVR in gray matter structures was 84%. Regionally, cerebellum (105%) showed significantly higher CVR than other regions (frontal cortices=70%, temporal cortices=75%, thalamus=75%, basal ganglia=88%, thalamus=84%, posterior cingulated gyrus=68%, parahippocampal gyrus=76%). Mean CVR for white matter (centrum semiovale=53%) was significantly lower than those of other brain structures (p<0.05).

Conclusions The present study indicated regional difference in the CVR in normal volunteers. When perfusion reserve is studied in patients with ischemic cerebrovascular diseases, regional CVR difference should be taken into account.

Research Support Global COE project, Japa